i've made my 5th batch of beer and never had bomb carboy.but this time just after 9-10 hours my airlock starts bubbling too fast ,i think i overpitched it.I'm afraid if it will explode !!?? should i do something ?

+1 on the tin foil. It can be sanitized with Starsan or Idophor spray before using. As long as the airlock is bubbling, it can't blow-up. Only if your airlock becomes completely plugged and can't vent can this become an issue. Keep a three foot piece of 1" blow off tube handy and know more worries.

Like others have posted it wont explode, but it can send the airlock flying and spew wort about 20ft in all directions one tip is to break the little plastic tip off of the bottom of the airlock the tip restricts the flow of wort spewing through and can get clogged usually if you do this the wort will flow out of the top of the airlock and down the carboy (better than blowing off). definitely save some old milk jusgs and go to home depot and get some hose. i use blow offs for all of my fermentation now